.pure-top {
  position: relative;
  z-index: 0;
  overflow: hidden;
}

.pure-top::after {
  content: '';
  width: 120%;
  height: 200px;
  position: absolute;
  left: -10%; // 椭圆左边隐藏10%，右边隐藏10%
  top: 0;
  border-radius: 0 0 50% 50%; // 左上角，右上角，右下角，左下角
  background: #1496f1;
}
